Hot start vent and flame arrester for carburetor



Sept. 26, 1967 J. o. SARTO HOT START VENT AND FLAME ARRESTER FOR CARBURETOR Filed Aug. 10, 1966 INVENTOR HTf RMZYZ United States Patent 3,343,819 HOT START VENT AND FLAME ARRESTER FOR CARBURETOR Jorma O. Sarto, Orchard Lake, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Aug. 10, 1966, Ser. No. 571,505 4 Claims. (Cl. 261-1) ABSTRACT OF THE DISCLOSURE A small diameter vent duct for venting fuel vapor from the induction conduit of an internal combustion engine when the latter is hot but not operating extends through the sidewall of the conduit at a location immediately above the throttle when the latter is closed. The vent duct terminates exteriorly of the induction conduit in a flame arrester for extinguishing flame in the event of backfire and to restrict the flow of air into the induction conduit via the vent duct during cranking and normal operation of the engine.

This invention relates to a fuel charging means of the customary down draft type of carburetor for an internal combustion engine and has for a principal object the provision of simple and effective means to enhance starting of the engine after being shut down for a few minutes in a hot condition.

When the conventional down draft carburetor is shut down in the hot condition, the throttle will be closed and fuel vapor from the primary fuel system will be discharged from the primary fuel nozzle into the induction conduit above the throttle valve. These vapors are heavier than air and accumulate above the closed valve, frequently displacing all the air in the induction conduit above the throttle valve and backing up to fill the comparatively large volume of induction conduit air horn and air filter with an incombustible charge of pure fuel vapor. Thereafter when an attempt is made to start the engine, the incombustible charge is drawn into the engine to delay its starting until it is cranked sufliciently to exhaust the incombustible charge.

In order to prevent the accumulation of such a charge, it is an object of the present invention to provide a small vent duct connecting the induction conduit, at a location immediately above the throttle valve in the closed position, with the atmosphere.

On occasion however, during engine starting with the throttle open, a backfire in the engine will blow flame backward in the induction conduit. It is accordingly another object to combine a flame arrester with the vent duct, the flame arrester comprising a tubular extension of the vent duct having a comparatively high coefficient of thermal conductivity and extending outwardly from the induction conduit into the atmosphere to such an extent that any flame initially blown from the induction conduit via the vent duet will be cooled in its passage through the tubular flame arrester and extinguished before it is exhausted to the atmosphere.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is a diagrammatic view of an automotive internal combustion engine adapted for use with the present invention.

FIG. 2 is a somewhat diagrammatic vertical sectional view through the induction conduit of the carburetor 3,343,819 Patented Sept. 26, 1967 shown in FIG. 1, illustrating an embodiment of the present invention.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring in more particularity to the drawings, a carburetor 10 is illustrated comprising three principal body sections including an upper air inlet and choke valve section 11, an intermediate venturi section 12, and a lower throttle section 13 suitably spaced by gaskets 14 and bolted together by means not specifically shown. The three carburetor sections cooperate to define an induction conduit 15 extending completely therethrough and adapted to align with a customary intake header 16 for conducting a combustible fuel and air mixture to the engine 17. The latter may comprise a conventional automotive internal combustion engine, so that details thereof are not shown.

The intermediate body portion 12 is formed with a large venturi 18 aligned coaxially with the conduit 15 and separated from an integral fuel bowl 19 by means of a transverse vertical wall 20. The fuel bowl 19' contains a supply of liquid fuel automatically maintained at approximately the level 21 by a float controlled inlet valve connected with a customary fuel pump. The top of the fuel bowl 19 is covered by an extension 22 of the upper body section 11 to provide a comparatively dust free fuel bowl enclosure which is vented by means of vent duct 23 to atmospheric pressure within conduit 15 above the conventional choke valve described below.

A throttle valve rod 24 is pivotally mounted in the conduit portion 15 of the throttle body section 13 and supports a throttle valve 25 operable in a conventional manner by a pedal actuated linkage. The lower body portion 13 is also formed with mounting flanges 26 to facilitate mounting of the carburetor assembly 10 on the intake manifold 16 as aforesaid.

An embossment 27 of the transverse wall 20 extends to the right to define a portion of the venturi 18 and is cored vertically to provide a fuel well 28. A small venturi 29 arranged coaxially upstream of the venturi 18 is provided with an integral extension 30 seated on the upper horizontal surface of the embossment 27.

The fuel well 28 extends upwardly into the extension 30 which in turn is provided with a recess 31, in communication with the fuel well 28, and a downwardly extending passage 32. The latter contains a tubular main fuel nozzle 33 pressed tightly therein and discharging into the throat region of the venturi 29. The upper end of the passage 32 communicates with the upper portion of the well 28 for receiving fuel therefrom during operation of the engine 17 under load.

A hollow vent or partitioning tube 34 is secured within the recess 31 by means of a press fit and extends down- Wardly into the well 28. The tube 34 is formed with a plurality of ports 35 spaced along its length to permit the transfer of air from its interior into the adjacent portions of the well 28 for emulsifying the fuel. Air is admitted into the hollow interior of the tube 34 at its upper end through a restricted port 36, which communicates with the air induction passage 15.

A second recess 37 is formed in the upper portion of the extension 30 to receive the upper end of an idle tube 38 pressed tightly therein. The idle tube 38 communicates with the bottom of the well 28 through an idle fuel inlet port 39 and communicates with a third recess 40 in the upper end of extension 30 by means of an upper transverse passage 41, the latter being defined in part by a port in the upper end of idle tube 38. The opening 40 extends vertically through the extension 30 in alignment with a lower threaded opening 42 in the wall 20. A hollow or tubular clamping bolt 43 is received snugly within the opening '40 and is screwed tightly into the opening 42 to clamp the projection 30 securely in place on the embossment 27. A fibrous gasket 44 is preferably disposed between the extension 30 and embossment 27.

The central bore of bolt 43 communicates upwardly through an idle air bleed restriction 45 with the air induction passage 15 to receive air for mixing with the idle fuel to provide a combustible fuel and air mixture for the engine 17 during idling. This idle fuel-air mixture is conducted through the bolt 43 to a communicating idle fuel passage 46 which extends downwardly into the throttle body section 13 and opens into the induction conduit 15 through an inwardly tapered conical idle port 47 located downstream of the throttle valve 25. The degree of restriction of the idle port 47 may be varied by a mating conical valve element 48 having an integral co axial screw threaded outer body 49 threadably connected to the lower body 13 and extending to the exterior thereof to permit manual adjustment.

The interior of the fuel bowl section 19 contains a main metering element 50 screwed into the base of the fuel bowl at 51. The metering element 50 is situated substantially at the plane of symmetry of the fuel bowl and is formed with a main metering orifice 52 communicating with a fuel supply passage 53 which discharges into the bottom of the fuel well 28. The upper portion of the metering element 50 slidably receives and guides a metering pin 54 carried by a vertically slidable piston 55 reciprocable within a cylinder 56. The piston 55 is biased upwardly by a coil spring 57 within the cylinder 56. The latter below the piston 55 is connected by duct 58 with the intake manifold conduit downstream of the throttle valve 25, so that the restriction of the main metering orifice 52 will be varied by the metering pin 54 as the piston 55 is adjusted vertically within the cylinder 56 in response to the engine manifold pressure.

Cooperating with the idle fuel system is a vertically slotted idle transfer port 59 in communication with the idle conduit 46 and opening into the sidewall of the conduit 15. Preferably the transfer slot 59 extends upwardly from its lower end, located at approximately the upper edge of the throttle blade 25 when the latter is in the closed or idle position shown, to its upper end slightly above the aforesaid upper edge of the throttle valve 25.

A choke rod 60 is pivotally mounted in the conduit portion 15 of the upper air horn or inlet section 11 and carries a pivotal unbalanced choke blade 61. The latter is urged to its closed position with a force which increases with decreasing temperature by means of a temperature controlled linkage comprising a dual crank arm member 62, connected with the choke rod 60 to pivot therewith, and a link 63. The dual crank arm member 62 has an interior arm extending radially from rod 60 within the conduit 15 and an exterior arm extending radially from rod 60 exteriorly of conduit 15. The link 63 is pivotally connected at its upper end with the outer end of the exterior arm of crank arm member 62 and is connected at its lower end with the free end of a bimetallic thermostatic spring 64.

The fixed end 65 of the latter is secured within a housing portion 66 responsive to a suitable engine operating temperature, so that as the engine temperature rises, the thermostatic spring force urging closing of the choke valve 61 decreases. Also pivotally connected to the outer swinging end of the interior arm of crank arm member 62 is a link 67 pivotally connected at its opposite end with a reciprocal plunger 68 which extends through a sidewall opening 69 in the upper body section 11 and is suitably secured at its outer endby clamping plates 70 to a flexible diaphragm 71. The latter is urged leftward in the drawing by means of a biasing spring 72,-so as to urge the choke valve 61 to the closed position illustrated in dotted lines. The diaphragm 71 defines one wall of a pressure chamber 73 which is connected by means of a conduit 74 with the induction conduit 15 at a location downstream of the throttle valve 25. In the present instance the chamber 73. is also defined in part by a housing 75 having footings 76 secured to body section 11.

The structure described thus far may relate to either a single or multiple barrel carburetor and may be conventional, reference being bad to Ball Patent No. 2,966,344 and to Sarto copending application Serial No. 368,193, as if the same were incorporated herein, for a more complete discussion of the structure and operation of the conventional details shown.

In operation, the fuel well 28 tends to be partially filled with fuel to the level 21 by means of the metering orifice 52 and conduit 53. When the throttle valve 25 is at the closed or idle position shown, the low pressure downstream of the valve 25 will actuate diaphragm 71 to pull the choke valve 61 to the partially open position shown against the closing force of the thermostatic spring 64, even under cold operating conditions.

Also the low pressure downstream of the throttle valve 25 will actuate piston 55 and pull the latter and plunger 54 downwardly to the idle position, so as to restrict the opening 52 in accordance with the idle operating conditions. The low pressure downstream of throttle valve 25 induces fluid flow via idle conduit 46 and port 47 into the induction conduit, whereupon fuel in the well 28 is forced upwardly through the idle tube 38 via idle supply port 39 to the duct 41 and thence into the bore of the hollow bolt 43 downwardly into the conduit 46. Similarly, air for supporting idle combustion will be supplied by controlled leakage around the throttle valve 20, through the restricted vent 45, and through the transfer port 59, which latter will be in the high pressure region of the conduit 15 by viture of the closed throttle 25 and the partially open choke valve 61, and thence via conduit 46 and port 47 into the induction conduit 15 to support engine idling.

As the throttle is initially opened progressively in accordance with increased engine load, the portion of the transfer port 59 downstream of the upper edge of the throttle blade 25 will progressively increase, thereby to decrease the pressure in idle conduit 46 and increase the fuel flow therethrough from idle tube 38 and into conduit 15 via both ports 47 and 59. As the throttle 25 continues to open to increase the air flow in codnuit 15, low pressure will be induced at the lower end of nozzle 33 by reason of the venturi system 18, 29 and fuel will be forced upwardly in well 28 to passage 32 and discharged via nozzle 33. Simultaneously, emulsifying air for the main fuel supply will be admitted into tube 34 via restriction 36 and admixed with the fuel in well 28 by means of ports 35. Finally, after continued opening of throttle 25, the pressure in conduit 15 at the ports 47 and 59 will rise sufficiently to prevent fuel flow in the idle system. As the air flow in conduit 15 increases, the downwardly flowing air frornthe customary air filter 77 impinging against the unbalanced choke buade 61 will force the latter open regardless that the increased pressure at the right of diaphragm 71 no longer urges opening of the choke valve 61. Also with the increasing pressure downstream of throttle 25 as the latter progressively opens, the metering rod 54 will be withdrawn from metering port 52 to progressively open the latter and increase the fuel flow into well 28.

If the engine 17 is shut olf after attaining its normal operating temperature, the customary engine cooling sys tem ceases to function and heat from the body of the engine causes overheating of the liquid fuel in bowl 19 and well 28, such that fuel vapor rises in well 23 and is discharged via nozzle 33 into conduit 15, as well as via bowl vent 23. During this condition, throttle valve 25 will be closed and thermostatically controlled choke 61 will be open. Accordingly the heavy fuel vapor tends to displace the air in conduit 15 above the throttle valve. In order to prevent fuel vapor accumulation in the air horn section 11 and the comparatively large volume of the air filter 77, a hot start vent duct 78 of small diameter is provided in the conduit 15 immediately above the lower edge of blade 25. The duct 78- preferably declines outwardly to facilitate gravity flow of the heavy fuel vapor and terminates in a tubular flame arrester 79 of material having a high coefiicient of thermal conductivity, such as copper by way of example, opening to the atmosphere. The ratio of the length of tube 79 with respect to its diameter is determined in accordance with its thermal properties so that in the event of an engine backfire with the throttle 25 open, flame tending to be blown through tube 79 will be cooled and extinguished by passage through tube 79, thereby to avoid the possibility of an under-the-hood fire. For a conventional carburetor for a passenger automobile, an inside diameter of approximately .03" to .06" has been found satisfactory for a copper tube 79 approximately 8 long. In order to confine the tube 79 in the space available, the tube may be coiled in a declining spiral of approximately one-half inch inner diameter, as illustrated. During engine cranking With the throttle open, low pressure within the conduit '15 will prevent the loss of fuel vapors through vent 78- 79 and in fact an inflow of air will result which will increase the pressure in conduit 15 and tend to result in a leaner fuel-air starting mixture. However the diameter of vent duct 78-79 is preferably comparatively small as aforesaid so that the effect of the hot start vent duct and flame arrester 78-79 on engine starting is nominal.

Having thus described my invention, I claim:

1. In a fuel charging device for an internal combustion engine, a fuel-air induction conduit for supplying a combustible fuel and air mixture to said engine, a throttle valve in said conduit, means for supplying fuel to said conduit at a location upstream of said throttle valve, means for venting fuel vapors from said conduit tending to accumulate therein upstream of said throttle valve when the latter is closed and said engine is not operating comprising a vent duct communicating with said conduit at a location adjacent and upstream of said throttle and opening to the atmosphere, said vent duct terminating in a flame arrester located exteriorly of said conduit for extinguishing flame in said vent duct in the event of a backfire in said conduit.

'2. In the combination according to claim 1, said flame arrester comprising a spiral tube of heat conducting mate rial declining throughout its length.

-3. -In the combination according to claim 1, said vent duct extending through the sidewall of said con-duit immediately upstream of said throttle valve when the latter is closed and comprising a tube of heat conducting material.

4. In the combination according to claim 3, the internal diameter of said flame arrester being dimensioned to effect significant resistance to the inlet flow of air into said induction conduit via said vent duct during normal engine operation.

References Cited UNITED STATES PATENTS 1,913,787 6/1933 Basseau 123142 2,012,000 8/1935 Eyssartier 123-142 2,690,331 9/1954 Weldy 261-1 HARRY B. THORNTON, Primary Examiner. TIM R. MILES, Assistant Examiner. 

1. IN A FUEL CHARGING DEVICE FOR AN INTERNAL COMBUSTION ENGINE, A FUEL-AIR INDUCTION CONDUIT FOR SUPPLYING A COMBUSTIBLE FUEL AND AIR MIXTURE TO SAID ENGINE, A THROTTLE VALVE IN SAID CONDUIT, MEANS FOR SUPPLYING FUEL TO SAID CONDUIT AT A LOCATION UPSTREAM OF SAID THROTTLE VALVE, MEANS FOR VENTING FUEL VAPORS FROM SAID CONDUIT TENDING TO ACCUMULATE THEREIN UPSTREAM OF SAID THROTTLE VALVE WHEN THE LATTER IS CLOSED AND SAID ENGINE IS NOT OPERATING COMPRIS- 